Bilateral asthenospheric flow fed by the Caroline plume (western Pacific Ocean)

The interaction of mantle plumes with plate tectonics is typically illustrated by hotspots and corresponding seamount chains, which exhibit age progression in line with absolute plate motions. However, the Caroline seamount chain in the western Pacific Ocean presents ambiguous features that challenge the classical hotspot hypothesis. We used waveform tomography to derive S-wave velocity and radial anisotropy models around the Caroline plate by fitting body and surface waves. Our findings reveal an elongated low-velocity anomaly in the asthenosphere beneath the Caroline seamount chain, accompanied by positive radial anisotropy. This anomaly is associated with a vertical low-velocity anomaly east of the middle of the chain, suggesting bilateral asthenospheric flow fed by the Caroline plume. This mechanism could explain age overlapping and prolonged volcanic activities in the Caroline Islands. We propose that a subducting slab acts as a barrier, redirecting the asthenospheric flow along thin lithosphere bilaterally. These observations shed new light on the interplay between plate tectonics and mantle plumes.